Introduction

Adobe Illustrator is an application that that provides tools you can use to work with vector graphics, which include vector shapes and vector objects. Vector graphics are created using mathematical shapes, not pixels, and that’s why vector shapes are considered resolution-independent. When you draw a vector object, you create one or more lines called a path. A path is made up of one or more curved or straight line segments. The start and end points for a line segment is known as an anchor point, which you can drag to change and move.

Illustrator provides drawing tools on the Tools panel that you can use to create a variety of shapes, including rectangles, rounded rectangles, ellipses, polygons, stars, flares, lines, arcs, spirals, rectangle grids, and polar (circular) grids. After you draw an object, you can use Illustrator selection tools to modify it. The two main selection tools are the Selection tool and the Direct Selection tool. The Selection tool allows you to select entire objects, while the Direct Selection tool allows you to select paths and segments. In addition to these tools, you can also use the Select menu. The Select menu provides a variety of powerful selection commands for you to use in a document or artboard. For example, you can select objects whose attributes (including Appearance, Blending Modes, Fill & Stroke, Opacity, and Stroke Color) are similar to the current or last selection.

After you select one or more objects, you can move, align, group, and transform them. The transformation tools allow you to rotate, scale (resize), reflect (mirror image), or shear (slant) an object.

Understanding Vector and Raster Graphics

Illustrator is an application that gives you great control over vector graphics, which include vector shapes and vector objects. Vector graphics are created using mathematical shapes, not pixels, and that’s why vector shapes are considered resolution-independent. For example, if you enlarge a vector image to 100 times its original size, Illustrator merely changes the mathematical formulas to reflect the new size, and since vector shapes are constructed of mathematical data instead of pixels, file sizes are extremely small.

Raster graphics, such as bitmaps and photographs, are images creating using individual pixels that identify one piece of color information. The reason raster images are considered resolution-dependent is that once the image is created or scanned, any enlargement of the image forces Illustrator to enlarge and average the existing color information in the document. This process, called interpolation, is what causes enlarged raster images to become blurred, or pixelated.

When you draw an object, you create one or more lines called a path. A path is made up of one or more curved or straight lines, known as segments. The start and end points for a segment is called an anchor point. An anchor point is a bending point to modify the line segment. A path can be open or closed. An open path has open-ended endpoints, such as a line, while a closed path has connected endpoints, such as a circle. Paths can have two types of anchor points: smooth points or corner points. A smooth point connects two curved segments to create a smooth line, while a corner point connects two straight or curved segments to create a path direction change. You can draw a path using both smooth and corner points. The outline of a path is called a stroke, which you can format with different characteristics. You can specify stroke weight (thickness), color, or a dashed pattern. The interior of an open or closed path is called a fill, which you can also format with a color or gradient.

You can change the shape of a path by dragging its anchor point. A selected anchor point or endpoint appears as a solid square, while an unselected one appears as a white square. When you select an anchor point with a curved segment, a direction line appears with direction points on each end, which you can drag to change the shape of the path. When you change the shape of a smooth point with curved segments on each side, both segments get changed. When you change a shape of a corner point, the corner is maintained, but adjusted based on the change.

Working with Anchor Points

In Illustrator, you can show or hide anchor points, direction lines, and direction points by choosing the View menu, and then choosing Show Edges or Hide Edges. If you want to show or hide direction lines for selected anchor points, select the Direct Selection tool, select the anchor point that you want, and then click Show Handles For Multiple Selected Anchor Points or Hide Handles For Multiple Selected Anchor Points button in the Control panel.

You can specify options in the Selection & Anchor Display preferences to always show handles when multiple anchor points are selected (this option is turned off by default).